Interaction of Methanol Spray and Water‐Deficit Stress on Photosynthesis and Biochemical Characteristics of Phaseolus vulgaris L. cv. Sadry

This study was a factorial experiment with a completely randomized design and three replications. The four levels of methanol spraying were used. Spraying was carried out three times during the growing season at 10‐day intervals beginning at 4 weeks after sowing. The spraying of solution continued until saturation of droplets on the leaves was achieved. The levels of water‐deficit stress applied were nonstress, moderate water stress and severe water stress. The results showed that there was a significant difference (P ≤ 0.05) between the methanol and water‐deficit stress treatments for chlorophyll (Chl) a and Chl b, carotenoid, total chlorophyll, net photosynthesis (P_N), intercellular CO₂ (C_i), maximal quantum yield of photosystem II photochemistry (F_v/F_m), leaf moisture, water use efficiency and relative water content. The application of foliar methanol at all levels of water‐deficit stress significantly decreased the catalase activity of the roots. Under all levels of water‐deficit stress, the 30% (v/v) methanol treatment significantly decreased peroxidase activity in the roots over that for the control. The results suggest that foliar application of methanol can decrease the negative effects of water‐deficit stress on Phaseolus vulgaris L. cv. Sadry.